Southern Doubles, Stars and Variables
SOUTHERN ASTRONOMICAL DELIGHTS : Presented by Andrew James
|PAGE DS 001
10 Mar 2009
|RA : 00h
Dec : -30° to -90°
Constellations : Phe, Hyi, Hor, Oct.
Best Observed : Aug - Jan (Text Ordered by RA)
|RA : 00h
Dec : -30° to -90°
SELECTED SOUTHERN DOUBLES and VARIABLES
|1923.50||44.43||0.385||0.800||142.0||40.3||282.1||Eggen (2) (1965)||4|
|2012.84||44.66||0.404||0.740||146.9||63.3||303.7||Mason & Hartkopt (2001c)||3|
B 8 / β3 Tucanae (00327-6302) is another whitish 5.14v magnitude star is β3 Tucanae, lies some 9.1′SW at PA 118°. It also shares similar proper motion with the main and wide ‘AC’ pair. Known as B 8, its duplicity was found by van den Bos in 1926. It remains ‘unsplitable’ in all amateur telescopes as the separation is merely 0.1 arcsec, which has remained the almost the same despite some twenty-four observations being made since 1964. Some evidence exists that the PA has reduced from 173° to 171° but this is likely reflects more random errors than any real motion for such a close system. Few observations since this date have been achieved but there is no doubt this is a binary system. Spectral class is given as A0V.
|Component||A||Aa||B||C||D||A||B||β1,2 - β3|
|Related Component||β1/ B7||β1||β1||β2||β2||β3/ B8||β3||β1|
|Postion Angle (deg)||---||---||151||169||280||---||171||117|
|True Sep (AU)||---||---||150||---||1260||---||4.7||25400|
(00323-6302) is a very faint pair that was discovered by
Luyten as recently as 1985 and appears in his proper motion
catalogue. Much interest has been with this pair as the
proximity to Beta Tucanae suggested association. The
parallax of 38.85±1.1mas gives the distance of
25.74±0.73pc or about 84ly. Furthermore, the proper
motion is 562.3 arcsec (or 9′ 22.8″) per
millennia and is presently moving towards the northeastern
PA of 101°
Sep. : 1.1 arcsec
P.A. : 131°
YEAR : 1985
Mag.A: 11.2 B : 14.5
Sp. A: ? B : ?
π : 38.85±1.1mas
Dist.: 25.74±0.73 pc.
Source: WDS04, Tycho
RST 10 (00310-6237) is another faint pair some 16'N of β Tucanae itself. Since measured in 1928 the PA shows indications of minor changes in the position angle, which is only +2°. At present the separation is 1.6 arcsec aligned along PA 97°. The magnitude of the component is a faint 11.3 and 11.4. RST 10 can be separated in 20cm, though I have no really suggestion of what aperture could separate this faint pair. Those with 10.5cm in good skies might like to try this pair for themselves. Little is known about this pair.
COO 3 (00445-6230), in Tucana, was discovered at the Cordoba Observatory in 1894. Surprisingly missed, especially or such a bright star, by Herschel, Dunlop and Russell, COO 3 is placed some 1.6°ENE of β Tucanae with the yellowish and yellow pair having its companion 2.3 arcsec away at PA 66°. The magnitudes are 6.31 and 8.01, but the three recent photometric observations give the Δm as 1.78. Since 1894 the PA has change by some 24° while the separation has decreased by 1.3 arcsec. The combined spectra is F5III-IV and it is likely the two are connected. Distance from the 11.89±0.67 parallax is 84.31±4.80pc.
COO 3 has a significant proper motion of 103.35 arcsec 100yr-1, and is moving almost eastward (PA 86.5°) from its current position. However, it is only about a quarter that of LDS 6092. A 10.5cm will clearly separate the two with a reasonable seeing night. Overall, an uncommonly beautiful pair.
Δ2 / Lambda (λ1) Tucanae (00524-6930) lies in southern Tucana some 3°N of the Small Magellanic Cloud, and is placed some 1.6°NNW of the globular cluster NGC 362. The general field contains three stars, λ1 A and λ1 B (Δ2) and λ2. All three stars appear yellow, with λ2 perhaps being deeper in colour. Not recognised as a pair, both λ1 and λ2 Tuc are separated by 13.5′E (PA 96°). λ1 is about 1.2 magnitudes brighter than the Δ2 pair. It seems that all three stars maybe associated as the c.p.m. is about the same order an in similar directions.
Δ2 itself is a moderately wide 6.67 and 7.56 magnitude yellow pair separated by some 20.4 arcsec along PA 82°, which should not be confused by the observer with the wider λ1, λ2 Tuc. Since discovery by Dunlop in 1826 but first measure by Herschel in 1834, the PA has increased by some 5° while the separation has reduced by some 2.1 arcsec. The primary is a gorgeous deep yellow which reminded me very much of the companion to p Eridani. It is odd that Dunlop describes by micrometric measurements for the separation as 6.62 arcsec., but the distance is certainly three times this value. This field contains few other stars but the pair does look magnificent in binoculars or small telescopes. A wonderful visual treat.
10 Mar 2009